Sciencemadness Discussion Board

Coloration / Staining

GreenD - 16-1-2012 at 13:32

HELLO!

I want a comprehensive list of all color changing solutions for identification of various compounds. It would help if these were biologically friendly!

1. In the presence of air Indoxyl oxidizes and dimerizes to form indigo. [Colorless -> indigo]

2. Iodine and potassium permanganate staining are common for TLC. Stains heavily conjugated molecules. Toxic.

3. Curcumin from turmeric is pH sensitive. It goes from yellow to orange at ph >8.4

4. Phenolphthalein - yay. Suspected carcinogen.

There are a ton of pH sensitive dyes, I'm more interested in dyes that are easily oxidized in air or when hydrated/dehydrated change color. In presence of some media become colored, etc.

#1 is my favorite so far.

The purpose of this is to simply have a colored reminder of timing that I can put on my arm :)

GreenD - 16-1-2012 at 14:17

5. Methylene blue is observed to oxidize very slowly in air, and quicker with a metal catalysts like iron. It also oxidizes carbohydrates in the presence of iron and pyrophosphate (ferro-pyrophosphate). This end product is a dark black or brown. 17% oxidation takes place on the order of 10-24 hours.

gutter_ca - 16-1-2012 at 16:45

Quote: Originally posted by GreenD  

The purpose of this is to simply have a colored reminder of timing that I can put on my arm :)


Sigh

GreenD - 16-1-2012 at 19:30

Quote: Originally posted by gutter_ca  
Quote: Originally posted by GreenD  

The purpose of this is to simply have a colored reminder of timing that I can put on my arm :)


Sigh


it isn't really, i have my reasons but unfortunately if I shared them I'd be murdered.

Please help me in surviving!

neptunium - 17-1-2012 at 19:12

wow!!! murdered?? really? where are you ? in Iran??

Panache - 19-1-2012 at 06:32

Quote: Originally posted by GreenD  

The purpose of this is to simply have a colored reminder of timing that I can put on my arm :)


sorry please explain (that was a pauline hansen reference for anyone not living in australia ten years ago)

GreenD - 19-1-2012 at 08:16

I just want a dye that is either oxidized in air and changes color or is photo-sensitive to visible light and changes color.

Look up zubbles - that is a good example.

GreenD - 19-1-2012 at 11:40

Wait a minute this doesn't make sense:

For instance, an amino group conjugated to an azo group (chromophore) via, for instance, a benzene ring, will form an aminoazo chromogen. The conjugated amino auxochrome shifts the absorption band of the azo group to longer wavelengths and increases the intensity of the absorption band. However, judicious placement of a sulfonic acid group to an amino azo chromogen is not conjugated, however, the electron withdrawing effect causes a shift of absorption to longer wavelengths.

Isn't an amino group electron donating? Or are both of them electron withdrawing?